The present invention relates to laminate bond strength detection and, more specifically, to a laminate bond strength detection apparatus, an assembly for detecting laminate bond strengths and a method of detecting a laminate bond strength of a printed circuit board (PCB).
In the production of PCBs, susceptibility of a given PCB to delamination failures due to solder assembly heat cycles is related to several factors including, but not limited to, the glass transition (Tg) properties of the PCB material and the manufacturing processes employed to form the PCB. In particular, in lead free solder assembly processes that are now most commonly used for PCB manufacturing, processing temperatures are higher than temperatures used in traditional tin/lead/eutectic soldering processes and thereby require more robust and expensive PCB lamination features. Also, since delamination during assembly is a function of a number of heat cycles employed through reflow assembly processing and since current processes used in PCB manufacturing may have high numbers of heat cycles for given PCBs, undetectable and unpredictable delamination defects can occur. Such delamination defects can result in latent field defects and product reliability problems.
Currently, destructive tests of small samples of functional PCBs or electrical tests are employed to identify delamination defects. The destructive tests can have associated costs, however, since sampling is usually done at the start of production and does not take into account drifts in process parameters. Also, even if a cross-section of a non-defective sample passes its tests, such testing would not gauge the potential variability of the non-defective sample. Electrical testing, meanwhile, may not identify delamination failures when such delamination failures are insufficient to break electrical connections on the PCBs or cause significant dielectric damage that may increase signal noise level at higher signal rates during optimal system function situations.